Device for measuring aberrations in an eye-type system

Abstract

Device for measuring aberrations in an eye includes, an illumination path with an illumination diaphragm and a test path, imaging member and elements for positioning the eye in relation to the imaging member, a stray reflection filter element, which is centered on the measurement axis of the imaging member, and elements for the optical conjugation of the pupil of the eye with the plane of the illumination diaphragm and the test plane. The illumination beam path converges at the center of the filtration element. The filtration element, the illumination path, the test path and the conjugation elements are all interdependent and positioned on a platform that can move in relation to the imaging member along the axis. The illumination diaphragm is off-center in relation to the axis such that stray light flux reflected by the imaging member is deflected from the test path by filtration element.

1. A device for measuring the aberrations in an eye-type system, comprising an illumination path with notably means for transmitting an illumination beam (FE) to form by backscattering on the retina of the eye a secondary light source and a test path with notably test means in a given test plane (PA) of the phase of the wave emitted by said secondary source and emerging from the eye, characterised in that it comprises moreover:
 imaging means (L 1 ) and eye-positioning means enabling in particular to position a predetermined plane of the eye in a focal plane of said imaging means, 
 a stray reflection filtering element (FLT) whereof the centre defines with the optical centre of the imaging means (L 1 ) a measurement axis (z), substantially centred on the pupil of the eye, 
 optical separation means (LM 1 ) placed on the measurement axis and defining the illumination path and the test path, 
 on the illumination path, an illumination diaphragm, of predetermined aperture, 
 optical conjugation means (L 2 , L 3 ) centred on the measurement axis and enabling optical conjugation between said predetermined plane of the eye, the plane of the illumination diaphragm and the test plane, 
 and characterised in that the illumination beam converges substantially at the centre of the filtering element (FLT), in that the filtering element, the illumination path, the test path, the separation means and the conjugation means are interdependent, placed on a platform (PTF 1 ) mobile relative to the imaging means (L 1 ) along the optical axis of said means (z), enabling adjustment, with respect to the ametropia of the eye, of the optical conjugation by said means (L 1 ) of the retina of the eye with the centre of the filtering element, and in that the illumination diaphragm is off-centre with respect to the measurement axis, so that the stray light flux reflected by the cornea of the eye, the imaging means (L 1 ) as well as any diopter situated between the filtering element and the cornea, is deflected from the test path by the filtering element (FLT). 
 
   
   
     2. A device according to  claim 1 , characterised in that the filtering element (FLT) is composed of a drilled opaque blade, the hole being centred on the measurement axis (z), of predetermined dimensions so that the illumination beam (FE) and the test beam (FA) focused substantially at the centre of said hole, are transmitted by the filtering element whereas the stray reflections are stopped by the opaque portion of the filtering element. 
   
   
     3. A device according to  claim 1 , characterised in that the filtering element (FLT) is virtual, formed by the image of an actual filtering element FLTO, said actual filtering element (FLTO) being placed on the test path VA. 
   
   
     4. A device according to  claim 3 , characterised in that the actual filtering element (FLTO) is formed of a drilled opaque blade. 
   
   
     5. A device according to  claim 2 , characterised in that the size of the hole of the opaque blade is controllable. 
   
   
     6. A device according to  claim 1 , characterised in that the filtering element (FLT) is composed of a drilled mirror, the hole being centred on the measurement axis (z), of predetermined dimensions so that the illumination beam (FE) and the test beam (FA) focused substantially at the centre of said hole, are transmitted by the filtering element whereas the stray reflections are deflected by the reflecting portion of the filtering element. 
   
   
     7. A device according to  claim 1 , characterised in that the filtering element (FLT) comprises a mirror centred on the measurement axis, of predetermined dimensions so that the illumination beam (FE) and the test beam (FA) focused substantially at the centre of said mirror, are reflected by the filtering element whereas the stray reflections are not deflected by said element. 
   
   
     8. A device according to  claim 1 , characterised in that it comprises moreover means (COM) for controlling said platform (PTF 1 ), connected to the test means, causing a displacement along the measurement axis (z) of the platform according to a predetermined function of the ametropia of the eye measured by said test means. 
   
   
     9. A device according to  claim 1 , characterised in that said eye-positioning means comprise notably an imaging path (VI) of the pupil of the eye (PO), with a lens (L 4 ) substantially centred on the measurement axis (z) and an imaging camera interdependent upon said platform (PTF 1 ) comprising a detector situated on a focal plane of said lens (L 4 ) and a display system. 
   
   
     10. A device according to  claim 9 , characterised in that the positioning means comprise moreover an illumination device of the eye formed of a set of light sources, whereas the position can be adjusted by tuning the image of said sources reflected by the cornea on the detector, thereby enabling to control the position of the plane tangent to the apex of the cornea of the eye. 
   
   
     11. A device according to  claim 9 , characterised in that the positioning means comprise moreover a quasi-punctual light source, centred on the measurement axis (z), and placed substantially at the focus of said lens (L 4 ), a mask formed of at least two apertures whereof at least one is off-centre with respect to the measurement axis, and located near said source, to form at least two light beams, a separating blade receiving said beams, the position being adjusted by controlling on the detector of the imaging path, the superimposition of the spots formed by the beams after reflection on the cornea of the eye, thus enabling controlled positioning of the plane tangent to the apex of the cornea of the eye. 
   
   
     12. A device according to  claim 9 , characterised in that the eye-positioning means comprise moreover on the display of the detector of the imaging path, means for tracking the lateral position of the pupil of the eye, enabling to adjust this lateral position with respect to the position of the illumination beam relative to the size of the pupil. 
   
   
     13. A device according to  claim 9 , characterised in that said positioning means comprise moreover means for moving the imaging means (L 1 ) and the platform (PTF 1 ), interdependently, in order to adjust the position of the eye. 
   
   
     14. A device according to  claim 1 , characterised in that the optical conjugation means comprise imaging means (L 2 ) on the test path, the test plane being confused with a focal plane of said imaging means, and imaging means (L 3 ) on the illumination path, the plane of the illumination diaphragm being confused with a focal plane of said imaging means, said means (L 3 ) also focusing the illumination beam at the centre of the filtering element (FLT). 
   
   
     15. A device according to  claim 1 , characterised in that the separation means comprise at least a first separating blade (LM 1 ), substantially with flat and parallel faces, tilted on the measurement axis (z), crossed by a portion of the illumination beam and reflecting a portion of the wave emerging from the eye towards the test path. 
   
   
     16. A device according to  claim 15 , characterised in that the reflection coefficient of said blade (LM 1 ) is greater than approximately 70%. 
   
   
     17. A device according to  claim 15 , characterised in that the thickness of said blade (LM 1 ) introduces on the illumination beam, a predetermined offset with respect to the measurement axis (z), so that failing said blade accidentally, the illumination beam does not go through the filtering element any longer. 
   
   
     18. A device according to  claim 1 , characterised in that it comprises moreover a fastening path, enabling to fix the direction of the patient's gaze whereof the eye is tested, and including an illuminated image and a lens (L 5 ), the lens conjugating substantially optically the image with the filtering element (FLT). 
   
   
     19. A device according to  claim 1 , characterised in that the test means comprise a Shack-Hartmann type wave-front analyser including notably a matrix of microlenses, a matrix detector, processing means, and the test plane corresponding to the plane of the microlens matrix. 
   
   
     20. A device according to  claim 1 , characterised in that the illumination path comprises moreover means for transmitting an illumination beam centred on the measurement axis (z), of predetermined diameter, converging at the centre of the filtering element (FLT), and in that the position of the platform (PTF 1 ) is adjusted along the measurement axis (z) for substantially optical conjugation by the imaging means (L 1 ) of the curvature centre of the cornea with the centre of the filtering element (FLT), enabling self-collimation of said illumination beam on the anterior face of the cornea, the flux reflected on said face being sent towards the test means (MA) in order to measure the topography of the cornea. 
   
   
     21. A device according to  claim 1 , characterised in that the illumination path comprises moreover means for transmitting an illumination beam centred on the measurement axis (z), of predetermined diameter, converging at the centre of the filtering element (FLT), and in that the imaging means comprise an additional and removable self-collimation system, enabling to focus said illumination beam (FE) at the curvature centre of the cornea, the flux reflected on the anterior face of the cornea being sent towards the test means (MA) in order to measure the topography of the cornea.